Associated with a trend toward miniaturization and high performance of an electronic device in recent years, in a printed wiring board, high wiring density and high integration have been developed. This steps up to demands for reliability improvement by enhancing the heat resistance of the laminated plate for wiring. In such an application, the laminated plate is required to have not only excellent heat resistance but also a low thermal expansion coefficient.
The laminated plate for a printed wiring board generally is formed by curing and integrating a resin composition mainly composed of an epoxy resin and a glass woven fabric. The epoxy resin is generally excellent in a balance among insulating properties, heat resistance, a cost, and the like. However, to respond to the request for improving of the heat resistance in accordance with the high-density packaging and the highly multi-layered structure of a printed wiring board of recent years, the improvement of the heat resistance is inevitably limited. The high coefficient of thermal expansion is attempted to be lowered by choosing an epoxy resin with an aromatic ring or by highly filling an inorganic filler such as silica (see Patent Document 1).
Associated with a trend toward being smaller and thinner in recent years, a package substrate for a semiconductor has a major problem of a warp caused by the difference between the coefficients of thermal expansion of a chip and a substrate at the time of component mounting or package assembling. This requires a low coefficient of thermal expansion to be lowered. However, the increased amount of the filler is known to cause the lowered insulation reliability due to moisture absorption, the insufficient adhesion between the resin composition layer and the wiring layer, and the failure of press molding.